Ok, I also had this this problem with my Selectric II, the fix is an easy one. However, DO NOT ADJUST ANYTHING. I know it is tempting to turn that screw that looks like it might help, but you may be causing more harm than good if you adjust it wrong and throw the whole timing of the machine off.​ I would start out with by cleaning the index mechanism. Take off the outer covers (if you don't know how to do this, just look up a video online; it'll explain better than I can) and look at the index mechanism. It's all of the parts that move when you press 'index' and make sure all of the linkages and moving parts are clean. Once they are, oil them if they need too and if that works, don't make any adjustments. Now, it may be that an adjustment may need to be made, as was the case with my Selectric. I'll post a picture of the linkage that I adjusted slightly to improve the indexing of the machine tomorrow. But just make sure that everything is clean and think before you make an adjustment. I'm sure someone else will give you advice. Also, if you got your machine serviced last year, shouldn't it be ok? Seems awfully odd that a Selectric serviced last year would be acting up like this...